Method and apparatus for video coding

ABSTRACT

Aspects of the disclosure provide method and apparatus for video coding. In some examples, an apparatus includes receiving circuitry and processing circuitry. The processing circuitry decodes, from a coded video bitstream, a syntax element for an adjusted version of an initial quantization parameter (QP) value at a picture level for a picture. The adjusted version is in a range with an upper boundary that is changed with a maximum QP value. Then, the processing circuitry determines the initial QP value of a segment (such as a slice, a tile, a group of tiles and the like) in the picture based on the syntax element and determines a QP value for a block in the segment according to the initial QP value of the segment and adjustments associated with the block. Then, the processing circuitry performs an inverse quantization on quantized data of the block according to the determined QP value.

INCORPORATION BY REFERENCE

This application is a continuation application of U.S. application Ser.No. 17/093,314, filed Nov. 9, 2020, which is a continuation applicationof U.S. application Ser. No. 16/727,704, filed Dec. 26, 2019, which is acontinuation application of U.S. application Ser. No. 16/198,966, filedNov. 23, 2018, and is based upon and claims the benefit of priority toU.S. Provisional Application No. 62/739,312, “INITIAL SLICE LEVEL QPOFFSET SETTING” filed on Sep. 30, 2018, the entire contents of each ofwhich are hereby incorporated herein by reference.

TECHNICAL FIELD

The present disclosure describes embodiments generally related to videocoding.

BACKGROUND

The background description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent the work is described in thisbackground section, as well as aspects of the description that may nototherwise qualify as prior art at the time of filing, are neitherexpressly nor impliedly admitted as prior art against the presentdisclosure.

Quantization parameter (QP) is one of the parameters to adjust the videoquality and bitrate levels. For example, a low QP value can result inmore information in the residual data and the coded video bitstreamrequires a high bitrate level; and a high QP value can result in loss ofinformation in the residual data, and the coded video bitstream requiresa low bitrate level.

SUMMARY

Aspects of the disclosure provide method and apparatus for video coding.In some examples, an apparatus includes receiving circuitry andprocessing circuitry. The processing circuitry decodes, from a codedvideo bitstream, a syntax element for an adjusted version of an initialquantization parameter (QP) value at a picture level for a picture. Theadjusted version is in a range with an upper boundary that is changedwith a maximum QP value. Then, the processing circuitry determines theinitial QP value of a segment (such as a slice, a tile, a group of tilesand the like) in the picture based on the syntax element and determinesa QP value for a block in the segment according to the initial QP valueof the segment and adjustments associated with the block. Then, theprocessing circuitry performs an inverse quantization on quantized dataof the block according to the determined QP value for the block.

In some embodiments, the processing circuitry decodes a segment levelchange for the initial QP value from the coded video bitstream, anddetermines the initial QP value for the segment according to the segmentlevel change. In an example, the syntax element for the adjusted versionof the initial QP value is decoded from a picture parameter set of thecoded video bitstream.

In an embodiment, the processing circuitry recovers the initial QP valuefrom the adjusted version of the initial QP value by adding a constantvalue. For example, the constant value is one of 26 or 28.

In another embodiment, the processing circuitry recovers the initial QPvalue from the adjusted version of the initial QP value based on themaximum QP value. For example, the processing circuitry recovers theinitial QP value from the adjusted version of the initial QP value byadding a half of the maximum QP value. In an example, the processingcircuitry bit-shifts the maximum QP value to right by one bit tocalculate the half of the maximum QP value. In another example, theprocessing circuitry bit-shifts a sum of the maximum QP value and one toright by one bit to calculate the half of the maximum QP value.

Aspects of the disclosure also provide a non-transitorycomputer-readable medium storing instructions which when executed by acomputer for video decoding cause the computer to perform the method forvideo coding.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, the nature, and various advantages of the disclosedsubject matter will be more apparent from the following detaileddescription and the accompanying drawings in which:

FIG. 1 is a schematic illustration of a simplified block diagram of acommunication system (100) in accordance with an embodiment.

FIG. 2 is a schematic illustration of a simplified block diagram of acommunication system (200) in accordance with an embodiment.

FIG. 3 is a schematic illustration of a simplified block diagram of adecoder in accordance with an embodiment.

FIG. 4 is a schematic illustration of a simplified block diagram of anencoder in accordance with an embodiment.

FIG. 5 shows a block diagram of an encoder in accordance with anotherembodiment.

FIG. 6 shows a block diagram of a decoder in accordance with anotherembodiment.

FIG. 7 shows a flow chart outlining a process example according to anembodiment of the disclosure.

FIG. 8 is a schematic illustration of a computer system in accordancewith an embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 illustrates a simplified block diagram of a communication system(100) according to an embodiment of the present disclosure. Thecommunication system (100) includes a plurality of terminal devices thatcan communicate with each other, via, for example, a network (150). Forexample, the communication system (100) includes a first pair ofterminal devices (110) and (120) interconnected via the network (150).In the FIG. 1 example, the first pair of terminal devices (110) and(120) performs unidirectional transmission of data. For example, theterminal device (110) may code video data (e.g., a stream of videopictures that are captured by the terminal device (110)) fortransmission to the other terminal device (120) via the network (150).The encoded video data can be transmitted in the form of one or morecoded video bitstreams. The terminal device (120) may receive the codedvideo data from the network (150), decode the coded video data torecover the video pictures and display video pictures according to therecovered video data. Unidirectional data transmission may be common inmedia serving applications and the like.

In another example, the communication system (100) includes a secondpair of terminal devices (130) and (140) that performs bidirectionaltransmission of coded video data that may occur, for example, duringvideoconferencing. For bidirectional transmission of data, in anexample, each terminal device of the terminal devices (130) and (140)may code video data (e.g., a stream of video pictures that are capturedby the terminal device) for transmission to the other terminal device ofthe terminal devices (130) and (140) via the network (150). Eachterminal device of the terminal devices (130) and (140) also may receivethe coded video data transmitted by the other terminal device of theterminal devices (130) and (140), and may decode the coded video data torecover the video pictures and may display video pictures at anaccessible display device according to the recovered video data.

In the FIG. 1 example, the terminal devices (110), (120), (130) and(140) may be illustrated as servers, personal computers and smart phonesbut the principles of the present disclosure may be not so limited.Embodiments of the present disclosure find application with laptopcomputers, tablet computers, media players and/or dedicated videoconferencing equipment. The network (150) represents any number ofnetworks that convey coded video data among the terminal devices (110),(120), (130) and (140), including for example wireline (wired) and/orwireless communication networks. The communication network (150) mayexchange data in circuit-switched and/or packet-switched channels.Representative networks include telecommunications networks, local areanetworks, wide area networks and/or the Internet. For the purposes ofthe present discussion, the architecture and topology of the network(150) may be immaterial to the operation of the present disclosureunless explained herein below.

FIG. 2 illustrates, as an example for an application for the disclosedsubject matter, the placement of a video encoder and a video decoder ina streaming environment. The disclosed subject matter can be equallyapplicable to other video enabled applications, including, for example,video conferencing, digital TV, storing of compressed video on digitalmedia including CD, DVD, memory stick and the like, and so on.

A streaming system may include a capture subsystem (213), that caninclude a video source (201), for example a digital camera, creating forexample a stream of video pictures (202) that are uncompressed. In anexample, the stream of video pictures (202) includes samples that aretaken by the digital camera. The stream of video pictures (202),depicted as a bold line to emphasize a high data volume when compared toencoded video data (204) (or coded video bitstreams), can be processedby an electronic device (220) that includes a video encoder (203)coupled to the video source (201). The video encoder (203) can includehardware, software, or a combination thereof to enable or implementaspects of the disclosed subject matter as described in more detailbelow. The encoded video data (204) (or encoded video bitstream (204)),depicted as a thin line to emphasize the lower data volume when comparedto the stream of video pictures (202), can be stored on a streamingserver (205) for future use. One or more streaming client subsystems,such as client subsystems (206) and (208) in FIG. 2 can access thestreaming server (205) to retrieve copies (207) and (209) of the encodedvideo data (204). A client subsystem (206) can include a video decoder(210), for example, in an electronic device (230). The video decoder(210) decodes the incoming copy (207) of the encoded video data andcreates an outgoing stream of video pictures (211) that can be renderedon a display (212) (e.g., display screen) or other rendering device (notdepicted). In some streaming systems, the encoded video data (204),(207), and (209) (e.g., video bitstreams) can be encoded according tocertain video coding/compression standards. Examples of those standardsinclude ITU-T Recommendation H.265. In an example, a video codingstandard under development is informally known as Versatile Video Codingor VVC. The disclosed subject matter may be used in the context of VVC.

It is noted that the electronic devices (220) and (230) can includeother components (not shown). For example, the electronic device (220)can include a video decoder (not shown) and the electronic device (230)can include a video encoder (not shown) as well.

FIG. 3 shows a block diagram of a video decoder (310) according to anembodiment of the present disclosure. The video decoder (310) can beincluded in an electronic device (330). The electronic device (330) caninclude a receiver (331) (e.g., receiving circuitry). The video decoder(310) can be used in the place of the video decoder (210) in the FIG. 2example.

The receiver (331) may receive one or more coded video sequences to bedecoded by the video decoder (310); in the same or another embodiment,one coded video sequence at a time, where the decoding of each codedvideo sequence is independent from other coded video sequences. Thecoded video sequence may be received from a channel (301), which may bea hardware/software link to a storage device which stores the encodedvideo data. The receiver (331) may receive the encoded video data withother data, for example, coded audio data and/or ancillary data streams,that may be forwarded to their respective using entities (not depicted).The receiver (331) may separate the coded video sequence from the otherdata. To combat network jitter, a buffer memory (315) may be coupled inbetween the receiver (331) and an entropy decoder/parser (320) (“parser(320)” henceforth). In certain applications, the buffer memory (315) ispart of the video decoder (310). In others, it can be outside of thevideo decoder (310) (not depicted). In still others, there can be abuffer memory (not depicted) outside of the video decoder (310), forexample to combat network jitter, and in addition another buffer memory(315) inside the video decoder (310), for example to handle playouttiming. When the receiver (331) is receiving data from a store/forwarddevice of sufficient bandwidth and controllability, or from anisosynchronous network, the buffer memory (315) may not be needed, orcan be small. For use on best effort packet networks such as theInternet, the buffer memory (315) may be required, can be comparativelylarge and can be advantageously of adaptive size, and may at leastpartially be implemented in an operating system or similar elements (notdepicted) outside of the video decoder (310).

The video decoder (310) may include the parser (320) to reconstructsymbols (321) from the coded video sequence. Categories of those symbolsinclude information used to manage operation of the video decoder (310),and potentially information to control a rendering device such as arender device (312) (e.g., a display screen) that is not an integralpart of the electronic device (330) but can be coupled to the electronicdevice (330), as was shown in FIG. 3 . The control information for therendering device(s) may be in the form of Supplementary EnhancementInformation (SEI messages) or Video Usability Information (VUI)parameter set fragments (not depicted). The parser (320) mayparse/entropy-decode the coded video sequence that is received. Thecoding of the coded video sequence can be in accordance with a videocoding technology or standard, and can follow various principles,including variable length coding, Huffman coding, arithmetic coding withor without context sensitivity, and so forth. The parser (320) mayextract from the coded video sequence, a set of subgroup parameters forat least one of the subgroups of pixels in the video decoder, based uponat least one parameter corresponding to the group. Subgroups can includeGroups of Pictures (GOPs), pictures, tiles, slices, macroblocks, CodingUnits (CUs), blocks, Transform Units (TUs), Prediction Units (PUs) andso forth. The parser (320) may also extract from the coded videosequence information such as transform coefficients, quantizer parametervalues, motion vectors, and so forth.

The parser (320) may perform entropy decoding/parsing operation on thevideo sequence received from the buffer memory (315), so as to createsymbols (321).

Reconstruction of the symbols (321) can involve multiple different unitsdepending on the type of the coded video picture or parts thereof (suchas: inter and intra picture, inter and intra block), and other factors.Which units are involved, and how, can be controlled by the subgroupcontrol information that was parsed from the coded video sequence by theparser (320). The flow of such subgroup control information between theparser (320) and the multiple units below is not depicted for clarity.

Beyond the functional blocks already mentioned, the video decoder (310)can be conceptually subdivided into a number of functional units asdescribed below. In a practical implementation operating undercommercial constraints, many of these units interact closely with eachother and can, at least partly, be integrated into each other. However,for the purpose of describing the disclosed subject matter, theconceptual subdivision into the functional units below is appropriate.

A first unit is the scaler/inverse transform unit (351). Thescaler/inverse transform unit (351) receives a quantized transformcoefficient as well as control information, including which transform touse, block size, quantization factor, quantization scaling matrices,etc. as symbol(s) (321) from the parser (320). The scaler/inversetransform unit (351) can output blocks comprising sample values, thatcan be input into aggregator (355).

In some cases, the output samples of the scaler/inverse transform (351)can pertain to an intra coded block; that is: a block that is not usingpredictive information from previously reconstructed pictures, but canuse predictive information from previously reconstructed parts of thecurrent picture. Such predictive information can be provided by an intrapicture prediction unit (352). In some cases, the intra pictureprediction unit (352) generates a block of the same size and shape ofthe block under reconstruction, using surrounding already reconstructedinformation fetched from the current picture buffer (358). The currentpicture buffer (358) buffers, for example, partly reconstructed currentpicture and/or fully reconstructed current picture. The aggregator(355), in some cases, adds, on a per sample basis, the predictioninformation the intra prediction unit (352) has generated to the outputsample information as provided by the scaler/inverse transform unit(351).

In other cases, the output samples of the scaler/inverse transform unit(351) can pertain to an inter coded, and potentially motion compensatedblock. In such a case, a motion compensation prediction unit (353) canaccess reference picture memory (357) to fetch samples used forprediction. After motion compensating the fetched samples in accordancewith the symbols (321) pertaining to the block, these samples can beadded by the aggregator (355) to the output of the scaler/inversetransform unit (351) (in this case called the residual samples orresidual signal) so as to generate output sample information. Theaddresses within the reference picture memory (357) from where themotion compensation prediction unit (353) fetches prediction samples canbe controlled by motion vectors, available to the motion compensationprediction unit (353) in the form of symbols (321) that can have, forexample X, Y, and reference picture components. Motion compensation alsocan include interpolation of sample values as fetched from the referencepicture memory (357) when sub-sample exact motion vectors are in use,motion vector prediction mechanisms, and so forth.

The output samples of the aggregator (355) can be subject to variousloop filtering techniques in the loop filter unit (356). Videocompression technologies can include in-loop filter technologies thatare controlled by parameters included in the coded video sequence (alsoreferred to as coded video bitstream) and made available to the loopfilter unit (356) as symbols (321) from the parser (320), but can alsobe responsive to meta-information obtained during the decoding ofprevious (in decoding order) parts of the coded picture or coded videosequence, as well as responsive to previously reconstructed andloop-filtered sample values.

The output of the loop filter unit (356) can be a sample stream that canbe output to the render device (312) as well as stored in the referencepicture memory (357) for use in future inter-picture prediction.

Certain coded pictures, once fully reconstructed, can be used asreference pictures for future prediction. For example, once a codedpicture corresponding to a current picture is fully reconstructed andthe coded picture has been identified as a reference picture (by, forexample, the parser (320)), the current picture buffer (358) can becomea part of the reference picture memory (357), and a fresh currentpicture buffer can be reallocated before commencing the reconstructionof the following coded picture.

The video decoder (310) may perform decoding operations according to apredetermined video compression technology in a standard, such as ITU-TRec. H.265. The coded video sequence may conform to a syntax specifiedby the video compression technology or standard being used, in the sensethat the coded video sequence adheres to both the syntax of the videocompression technology or standard and the profiles as document in thevideo compression technology or standard. Specifically, a profile canselect a certain tools as the only tools available for use under thatprofile from all the tools available in the video compression technologyor standard. Also necessary for compliance can be that the complexity ofthe coded video sequence is within bounds as defined by the level of thevideo compression technology or standard. In some cases, levels restrictthe maximum picture size, maximum frame rate, maximum reconstructionsample rate (measured in, for example megasamples per second), maximumreference picture size, and so on. Limits set by levels can, in somecases, be further restricted through Hypothetical Reference Decoder(HRD) specifications and metadata for HRD buffer management signaled inthe coded video sequence.

In an embodiment, the receiver (331) may receive additional (redundant)data with the encoded video. The additional data may be included as partof the coded video sequence(s). The additional data may be used by thevideo decoder (310) to properly decode the data and/or to moreaccurately reconstruct the original video data. Additional data can bein the form of, for example, temporal, spatial, or signal noise ratio(SNR) enhancement layers, redundant slices, redundant pictures, forwarderror correction codes, and so on.

FIG. 4 shows a block diagram of a video encoder (403) according to anembodiment of the present disclosure. The video encoder (403) isincluded in an electronic device (420). The electronic device (420)includes a transmitter (440) (e.g., transmitting circuitry). The videoencoder (403) can be used in the place of the video encoder (203) in theFIG. 2 example.

The video encoder (403) may receive video samples from a video source(401)(that is not part of the electronic device (420) in the FIG. 4example) that may capture video image(s) to be coded by the videoencoder (403). In another example, the video source (401) is a part ofthe electronic device (420).

The video source (401) may provide the source video sequence to be codedby the video encoder (403) in the form of a digital video sample streamthat can be of any suitable bit depth (for example: 8 bit, 10 bit, 12bit, . . . ), any colorspace (for example, BT.601 Y CrCB, RGB, . . . )and any suitable sampling structure (for example Y CrCb 4:2:0, Y CrCb4:4:4). In a media serving system, the video source (401) may be astorage device storing previously prepared video. In a videoconferencingsystem, the video source (401) may be a camera that captures local imageinformation as a video sequence. Video data may be provided as aplurality of individual pictures that impart motion when viewed insequence. The pictures themselves may be organized as a spatial array ofpixels, wherein each pixel can comprise one or more samples depending onthe sampling structure, color space, etc. in use. A person skilled inthe art can readily understand the relationship between pixels andsamples. The description below focusses on samples.

According to an embodiment, the video encoder (403) may code andcompress the pictures of the source video sequence into a coded videosequence (443) in real time or under any other time constraints asrequired by the application. Enforcing appropriate coding speed is onefunction of a controller (450). In some embodiments, the controller(450) controls other functional units as described below and isfunctionally coupled to the other functional units. The coupling is notdepicted for clarity. Parameters set by the controller (450) can includerate control related parameters (picture skip, quantizer, lambda valueof rate-distortion optimization techniques, . . . ), picture size, groupof pictures (GOP) layout, maximum motion vector search range, and soforth. The controller (450) can be configured to have other suitablefunctions that pertain to the video encoder (403) optimized for acertain system design.

In some embodiments, the video encoder (403) is configured to operate ina coding loop. As an oversimplified description, in an example, thecoding loop can include a source coder (430) (e.g., responsible forcreating symbols, such as a symbol stream, based on an input picture tobe coded, and a reference picture(s)), and a (local) decoder (433)embedded in the video encoder (403). The decoder (433) reconstructs thesymbols to create the sample data in a similar manner as a (remote)decoder also would create (as any compression between symbols and codedvideo bitstream is lossless in the video compression technologiesconsidered in the disclosed subject matter). The reconstructed samplestream (sample data) is input to the reference picture memory (434). Asthe decoding of a symbol stream leads to bit-exact results independentof decoder location (local or remote), the content in the referencepicture memory (434) is also bit exact between the local encoder andremote encoder. In other words, the prediction part of an encoder “sees”as reference picture samples exactly the same sample values as a decoderwould “see” when using prediction during decoding. This fundamentalprinciple of reference picture synchronicity (and resulting drift, ifsynchronicity cannot be maintained, for example because of channelerrors) is used in some related arts as well.

The operation of the “local” decoder (433) can be the same as of a“remote” decoder, such as the video decoder (310), which has alreadybeen described in detail above in conjunction with FIG. 3 . Brieflyreferring also to FIG. 3 , however, as symbols are available andencoding/decoding of symbols to a coded video sequence by an entropycoder (445) and the parser (320) can be lossless, the entropy decodingparts of the video decoder (310), including the buffer memory (315), andparser (320) may not be fully implemented in the local decoder (433).

An observation that can be made at this point is that any decodertechnology except the parsing/entropy decoding that is present in adecoder also necessarily needs to be present, in substantially identicalfunctional form, in a corresponding encoder. For this reason, thedisclosed subject matter focuses on decoder operation. The descriptionof encoder technologies can be abbreviated as they are the inverse ofthe comprehensively described decoder technologies. Only in certainareas a more detail description is required and provided below.

During operation, in some examples, the source coder (430) may performmotion compensated predictive coding, which codes an input picturepredictively with reference to one or more previously-coded picture fromthe video sequence that were designated as “reference pictures”. In thismanner, the coding engine (432) codes differences between pixel blocksof an input picture and pixel blocks of reference picture(s) that may beselected as prediction reference(s) to the input picture.

The local video decoder (433) may decode coded video data of picturesthat may be designated as reference pictures, based on symbols createdby the source coder (430). Operations of the coding engine (432) mayadvantageously be lossy processes. When the coded video data may bedecoded at a video decoder (not shown in FIG. 4 ), the reconstructedvideo sequence typically may be a replica of the source video sequencewith some errors. The local video decoder (433) replicates decodingprocesses that may be performed by the video decoder on referencepictures and may cause reconstructed reference pictures to be stored inthe reference picture cache (434). In this manner, the video encoder(403) may store copies of reconstructed reference pictures locally thathave common content as the reconstructed reference pictures that will beobtained by a far-end video decoder (absent transmission errors).

The predictor (435) may perform prediction searches for the codingengine (432). That is, for a new picture to be coded, the predictor(435) may search the reference picture memory (434) for sample data (ascandidate reference pixel blocks) or certain metadata such as referencepicture motion vectors, block shapes, and so on, that may serve as anappropriate prediction reference for the new pictures. The predictor(435) may operate on a sample block-by-pixel block basis to findappropriate prediction references. In some cases, as determined bysearch results obtained by the predictor (435), an input picture mayhave prediction references drawn from multiple reference pictures storedin the reference picture memory (434).

The controller (450) may manage coding operations of the source coder(430), including, for example, setting of parameters and subgroupparameters used for encoding the video data.

Output of all aforementioned functional units may be subjected toentropy coding in the entropy coder (445). The entropy coder (445)translates the symbols as generated by the various functional units intoa coded video sequence, by lossless compressing the symbols according totechnologies known to a person skilled in the art as, for exampleHuffman coding, variable length coding, arithmetic coding, and so forth.

The transmitter (440) may buffer the coded video sequence(s) as createdby the entropy coder (445) to prepare for transmission via acommunication channel (460), which may be a hardware/software link to astorage device which would store the encoded video data. The transmitter(440) may merge coded video data from the video coder (403) with otherdata to be transmitted, for example, coded audio data and/or ancillarydata streams (sources not shown).

The controller (450) may manage operation of the video encoder (403).During coding, the controller (450) may assign to each coded picture acertain coded picture type, which may affect the coding techniques thatmay be applied to the respective picture. For example, pictures oftenmay be assigned as one of the following picture types:

An Intra Picture (I picture) may be one that may be coded and decodedwithout using any other picture in the sequence as a source ofprediction. Some video codecs allow for different types of Intrapictures, including, for example Independent Decoder Refresh (“IDR”)Pictures. A person skilled in the art is aware of those variants of Ipictures and their respective applications and features.

A Predictive picture (P picture) may be one that may be coded anddecoded using intra prediction or inter prediction using at most onemotion vector and reference index to predict the sample values of eachblock.

A Bi-directionally Predictive Picture (B Picture) may be one that may becoded and decoded using intra prediction or inter prediction using atmost two motion vectors and reference indices to predict the samplevalues of each block. Similarly, multiple-predictive pictures can usemore than two reference pictures and associated metadata for thereconstruction of a single block.

Source pictures commonly may be subdivided spatially into a plurality ofsample blocks (for example, blocks of 4×4, 8×8, 4×8, or 16×16 sampleseach) and coded on a block-by-block basis. Blocks may be codedpredictively with reference to other (already coded) blocks asdetermined by the coding assignment applied to the blocks' respectivepictures. For example, blocks of I pictures may be codednon-predictively or they may be coded predictively with reference toalready coded blocks of the same picture (spatial prediction or intraprediction). Pixel blocks of P pictures may be coded predictively, viaspatial prediction or via temporal prediction with reference to onepreviously coded reference pictures. Blocks of B pictures may be codedpredictively, via spatial prediction or via temporal prediction withreference to one or two previously coded reference pictures.

The video encoder (403) may perform coding operations according to apredetermined video coding technology or standard, such as ITU-T Rec.H.265. In its operation, the video encoder (403) may perform variouscompression operations, including predictive coding operations thatexploit temporal and spatial redundancies in the input video sequence.The coded video data, therefore, may conform to a syntax specified bythe video coding technology or standard being used.

In an embodiment, the transmitter (440) may transmit additional datawith the encoded video. The source coder (430) may include such data aspart of the coded video sequence. Additional data may comprisetemporal/spatial/SNR enhancement layers, other forms of redundant datasuch as redundant pictures and slices, Supplementary EnhancementInformation (SEI) messages, Visual Usability Information (VUI) parameterset fragments, and so on.

A video may be captured as a plurality of source pictures (videopictures) in a temporal sequence. Intra-picture prediction (oftenabbreviated to Intra prediction) makes uses of spatial correlation in agiven picture, and inter-picture prediction makes uses of the (temporalor other) correlation between the pictures. In an example, a specificpicture under encoding/decoding, which is referred to as a currentpicture, is partitioned into blocks. When a block in the current pictureis similar to a reference block in a previously coded and still bufferedreference picture in the video, the block in the current picture can becoded by a vector that is referred to as a motion vector. The motionvector points to the reference block in the reference picture, and canhave a third dimension identifying the reference picture, in casemultiple reference pictures are in use.

In some embodiments, a bi-prediction technique can be used in theinter-picture prediction. According to the bi-prediction technique, tworeference pictures, such as a first and a second reference picture thatare both prior in decoding order to the current picture in the video(but may be in the past and future, respectively, in display order) areused. A block in the current picture can be coded by a first motionvector that points to a first reference block in the first referencepicture, and a second motion vector that points to a second referenceblock in the second reference picture. The block can be predicted by acombination of the first reference block and the second reference block.

Further, a merge mode technique can be used in the inter-pictureprediction to improve coding efficiency.

According to some embodiments of the disclosure, predictions, such asinter-picture predictions and intra-picture predictions are performed inthe unit of blocks. For example, according to the HEVC standard, apicture in a sequence of video pictures is partitioned into coding treeunits (CTU) for compression, the CTUs in a picture have the same size,such as 64×64 pixels, 32×32 pixels, or 16×16 pixels. In general, a CTUincludes three coding tree blocks (CTBs), which are one luma CTB and twochroma CTBs. Each CTU can be recursively quadtree split into one ormultiple coding units (CUs). For example, a CTU of 64×64 pixels can besplit into one CU of 64×64 pixels, or 4 CUs of 32×32 pixels, or 16 CUsof 16×16 pixels. In an example, each CU is analyzed to determine aprediction type for the CU, such as an inter prediction type or an intraprediction type. The CU is split into one or more prediction units (PUs)depending on the temporal and/or spatial predictability. Generally, eachPU includes a luma prediction block (PB), and two chroma PBs. In anembodiment, a prediction operation in coding (encoding/decoding) isperformed in the unit of a prediction block. Using a luma predictionblock as an example of a prediction block, the prediction block includesa matrix of values (e.g., luma values) for pixels, such as 8×8 pixels,16×16 pixels, 8×16 pixels, 16×8 pixels and the like.

FIG. 5 shows a diagram of a video encoder (503) according to anotherembodiment of the disclosure. The video encoder (503) is configured toreceive a processing block (e.g., a prediction block) of sample valueswithin a current video picture in a sequence of video pictures, andencode the processing block into a coded picture that is part of a codedvideo sequence. In an example, the video encoder (503) is used in theplace of the video encoder (203) in the FIG. 2 example.

In an HEVC example, the video encoder (503) receives a matrix of samplevalues for a processing block, such as a prediction block of 8×8samples, and the like. The video encoder (503) determines whether theprocessing block is best coded using intra mode, inter mode, orbi-prediction mode using, for example, rate-distortion optimization.When the processing block is to be coded in intra mode, the videoencoder (503) may use an intra prediction technique to encode theprocessing block into the coded picture; and when the processing blockis to be coded in inter mode or bi-prediction mode, the video encoder(503) may use an inter prediction or bi-prediction technique,respectively, to encode the processing block into the coded picture. Incertain video coding technologies, merge mode can be an inter pictureprediction submode where the motion vector is derived from one or moremotion vector predictors without the benefit of a coded motion vectorcomponent outside the predictors. In certain other video codingtechnologies, a motion vector component applicable to the subject blockmay be present. In an example, the video encoder (503) includes othercomponents, such as a mode decision module (not shown) to determine themode of the processing blocks.

In the FIG. 5 example, the video encoder (503) includes the interencoder (530), an intra encoder (522), a residue calculator (523), aswitch (526), a residue encoder (524), a general controller (521) and anentropy encoder (525) coupled together as shown in FIG. 5 .

The inter encoder (530) is configured to receive the samples of thecurrent block (e.g., a processing block), compare the block to one ormore reference blocks in reference pictures (e.g., blocks in previouspictures and later pictures), generate inter prediction information(e.g., description of redundant information according to inter encodingtechnique, motion vectors, merge mode information), and calculate interprediction results (e.g., predicted block) based on the inter predictioninformation using any suitable technique. In some examples, thereference pictures are decoded reference pictures that are decoded basedon the encoded video information.

The intra encoder (522) is configured to receive the samples of thecurrent block (e.g., a processing block), in some cases compare theblock to blocks already coded in the same picture, generate quantizedcoefficients after transform and, in some cases also intra predictioninformation (e.g., an intra prediction direction information accordingto one or more intra encoding techniques). In an example, the intraencoder (522) also calculates intra prediction results (e.g., predictedblock) based on the intra prediction information and reference blocks inthe same picture.

The general controller (521) is configured to determine general controldata and control other components of the video encoder (503) based onthe general control data. In an example, the general controller (521)determines the mode of the block, and provides a control signal to theswitch (526) based on the mode. For example, when the mode is the intra,the general controller (521) controls the switch (526) to select theintra mode result for use by the residue calculator (523), and controlsthe entropy encoder (525) to select the intra prediction information andinclude the intra prediction information in the bitstream; and when themode is the inter mode, the general controller (521) controls the switch(526) to select the inter prediction result for use by the residuecalculator (523), and controls the entropy encoder (525) to select theinter prediction information and include the inter predictioninformation in the bitstream.

The residue calculator (523) is configured to calculate a difference(residue data) between the received block and prediction resultsselected from the intra encoder (522) or the inter encoder (530). Theresidue encoder (524) is configured to operate based on the residue datato encode the residue data to generate the transform coefficients. In anexample, the residue encoder (524) is configured to convert the residuedata in the frequency domain, and generate the transform coefficients.The transform coefficients are then subject to quantization processingto obtain quantized transform coefficients. In various embodiments, thevideo encoder (503) also includes a residue decoder (528). The residuedecoder (528) is configured to perform inverse-transform, and generatethe decoded residue data. The decoded residue data can be suitably usedby the intra encoder (522) and the inter encoder (530). For example, theinter encoder (530) can generate decoded blocks based on the decodedresidue data and inter prediction information, and the intra encoder(522) can generate decoded blocks based on the decoded residue data andthe intra prediction information. The decoded blocks are suitablyprocessed to generate decoded pictures and the decoded pictures can bebuffered in a memory circuit (not shown) and used as reference picturesin some examples.

The entropy encoder (525) is configured to format the bitstream toinclude the encoded block. The entropy encoder (525) is configured toinclude various information according to a suitable standard, such asHEVC standard. In an example, the entropy encoder (525) is configured toinclude the general control data, the selected prediction information(e.g., intra prediction information or inter prediction information),the residue information, and other suitable information in thebitstream. Note that, according to the disclosed subject matter, whencoding a block in the merge submode of either inter mode orbi-prediction mode, there is no residue information.

FIG. 6 shows a diagram of a video decoder (610) according to anotherembodiment of the disclosure. The video decoder (610) is configured toreceive a coded pictures that are part of a coded video sequence, anddecode the coded picture to generate a reconstructed picture. In anexample, the video decoder (610) is used in the place of the videodecoder (210) in the FIG. 2 example.

In the FIG. 6 example, the video decoder (610) includes an entropydecoder (671), an inter decoder (680), a residue decoder (673), areconstruction module (674), and an intra decoder (672) coupled togetheras shown in FIG. 6 .

The entropy decoder (671) can be configured to reconstruct, from thecoded picture, certain symbols that represent the syntax elements ofwhich the coded picture is made up. Such symbols can include, forexample, the mode in which a block is coded (such as, for example,intra, inter, b-predicted, the latter two in merge submode or anothersubmode), prediction information (such as, for example, intra predictioninformation or inter prediction information) that can identify certainsample or metadata that is used for prediction by the intra decoder(672) or the inter decoder (680) respectively residual information inthe form of, for example, quantized transform coefficients, and thelike. In an example, when the prediction mode is inter or bi-predictedmode, the inter prediction information is provided to the inter decoder(680); and when the prediction type is the intra prediction type, theintra prediction information is provided to the intra decoder (672). Theresidual information can be subject to inverse quantization and isprovided to the residue decoder (673).

The inter decoder (680) is configured to receive the inter predictioninformation, and generate inter prediction results based on the interprediction information.

The intra decoder (672) is configured to receive the intra predictioninformation, and generate prediction results based on the intraprediction information.

The residue decoder (673) is configured to perform inverse quantizationto extract de-quantized transform coefficients, and process thede-quantized transform coefficients to convert the residual from thefrequency domain to the spatial domain. The residue decoder (673) mayalso require certain control information (to include the QuantizerParameter QP), and that information may be provided by the entropydecoder (671) (datapath not depicted as this may be low volume controlinformation only).

The reconstruction module (674) is configured to combine, in the spatialdomain, the residual as output by the residue decoder (673) and theprediction results (as output by the inter or intra prediction modulesas the case may be) to form a reconstructed block, that may be part ofthe reconstructed picture, which in turn may be part of thereconstructed video. It is noted that other suitable operations, such asa deblocking operation and the like, can be performed to improve thevisual quality.

It is noted that the video encoders (203), (403) and (503), and thevideo decoders (210), (310) and (610) can be implemented using anysuitable technique. In an embodiment, the video encoders (203), (403)and (503), and the video decoders (210), (310) and (610) can beimplemented using one or more integrated circuits. In anotherembodiment, the video encoders (203), (403) and (403), and the videodecoders (210), (310) and (610) can be implemented using one or moreprocessors that execute software instructions.

Aspects of the disclosure provide techniques to set default quantizationparameter (QP) values at a segment level. In an example, the segment canbe a slice, a tile, a group of tiles and other suitable segmentations.While slice is used in some examples, the examples can be suitablymodified for other segmentations, such as a tile, a group of tiles, andthe like. In some embodiments, the techniques are used in advanced videocodec to set an initial default QP value for the entire slice.

In an example, QP value is in a range from 0 to 51 inclusive. HEVCdefines a couple of syntaxes related to QP, such asbit_depth_luma_minus8, init_qp_minus26, slice_qp_delta and the like.

The syntax bit_depth_luma_minus8 specifies the bit depth of the samplesof the luma array BitDepthY and the value of the luma quantizationparameter range offset QpBdOffsetY as shown in Eq. 1 and Eq. 2BitDepth_(Y)=8+bit_depth_luma_minus8  Eq. 1QpBdOffset_(Y)=6×bit_depth_luma_minus8  Eq. 2

In an example, the syntax init_qp_minus26 can be used to specify theinitial value for slice level QP SliceQpy. For example, init_qp_minus26plus 26 specifies the initial value of SliceQp_(Y) for each slice thatrefers to the picture parameter set (PPS). The initial value ofSliceQp_(Y) is modified at the slice segment layer when a non-zero valueof slice_qp_delta is decoded. The value of init_qp_minus26 shall be inthe range of −(26+QpBdOffset_(Y)) to +25, inclusive. It is noted thatinit_qp_minus26 is signaled at PPS level in HEVC. When the decoderdecodes the syntex element init_qp_minus26, the decoder adds the 26 withthe init_qp_minus26 to determine the initial value of SliceQpy in anexample.

The syntax slice_qp_delta specifies the initial modification value(initial changes) of QpY to be used for the coding blocks in the slicesegment layer until modified by the value of CuQpDeltaVal in the codingunit layer. The initial value of the QpY quantization parameter for theslice, SliceQpY, is derived as Eq. 3SliceQp _(Y)=26+init_qp_minus26+slice_qp_delta  Eq. 3It is noted that the value of SliceQpY shall be in the range of−QpBdOffsetY to +51, inclusive. In an example, when the decoder decodesthe intia_qp_minus26 and the nonzero slice_qp_delta, the decodercalculates the initial value of QpY for the slice according to Eq. 3.

According to some aspects of the disclosure, when the dynamic range ofQP values supported in the standard or codec has been changed, theinitial or default QP value at slice level is suitably adjusted.

According to an aspect of the disclosure, the initial slice level QPvalue is adjusted according to the supported maximum QP value. In anembodiment, when the supported maximum QP value is maxQP (an oddpositive integer number), the initial slice level QP value can be setaccording to half of this value, for example, (maxQP+1)>>1. In anotherexample, half of the maximum QP value can be set as maxQP>>1. Thesignaled syntax element init_qp_minusXX (XX refers to the adjustedinitial slice level QP value) can be set as the real initial slice levelQP value minus the above half of the maximum value, i.e., minus((maxQP+1)>>1). Then the value of init_qp_minusXX is constrained in therange of −((maxQP>>1)+QpBdOffset_(Y)) to +((maxQP+1)>>1), inclusive. Orin another example, the value of init_qp_minusXX is constrained in therange of −(((maxQP+1)>>1)+QpBdOffset_(Y)) to +(maxQP>>1), inclusive.Accordingly, at the decoder side, the decoder decodes the syntax elementinit_qp_minusXX, calculates half of the maximum QP value ((maxQP+1)>>1or maxQP>>1), and calculates a sum of init_qp_minusXX and the half ofthe maximum QP value. The decoder then sets the initial slice level QPvalue according to the sum.

In another embodiment, when the supported maximum QP value is maxQP (anodd positive integer number), the initial slice level QP value can beset according to a default constant, for example, 26, or 28. Thesignaled syntax element initial_qp_minusXX (XX refers to the initialslice level QP value, for example, 26, or 28) can be set as the realinitial slice level QP value minus the above default constant, i.e.,minus 26 or minus 28. Then the value of init_qp_minusXX is constrainedin the range of −(XX+QpBdOffsetY) to +(maxQP-XX), inclusive.Accordingly, at the decoder side, the decoder decodes the syntax elementinit_qp_minus28 for example, and adds 28 to the init_qp_minus28 tocalculate the initial slice level QP value.

In an example, the maximum possible QP value is 63. In one embodiment,the initial QP value at slice level is set according to half of themaximum QP value ((maxQP+1)>>1) which equals 32, and then syntaxesinit_qp_minus32, slice_qp_delta are defined.

The syntax init_qp_minus32 plus 32 specifies the initial value ofSliceQp_(Y) for each slice referring to the PPS. The initial value ofSliceQp_(Y) is modified at the slice segment layer when a non-zero valueof slice_qp_delta is decoded. The value of init_qp_minus32 shall be inthe range of −(32+QpBdOffset_(Y)) to +31, inclusive.

The syntax slice_qp_delta specifies the initial modification value ofQp_(Y) to be used for the coding blocks in the slice until modified bythe value of CuQpDeltaVal in the coding unit layer. The initial value ofthe Qp_(Y) quantization parameter for the slice, SliceQp_(Y), is derivedas Eq. 4SliceQp _(Y)=32+init_qp_minus32+slice_qp_delta  Eq. 4The value of SliceQpY shall be in the range of −QpBdOffsetY to +63,inclusive. In an example, the decoder decodes the syntax elementsinit_qp_minus32 and the slice_qp_delta, and uses Eq. 4 to calculate theinitial value for the slice level QP.

In another embodiment, the initial QP value at slice level is setaccording to half of the maximum QP value (maxQP>>1) which is 31, andthen the syntaxes init_qp_minus31, and slice_qp_delta are defined.

The syntax init_qp_minus31 plus 31 specifies the initial value ofSliceQp_(Y) for each slice referring to the PPS. The initial value ofSliceQp_(Y) is modified at the slice segment layer when a non-zero valueof slice_qp_delta is decoded. The value of init_qp_minus31 shall be inthe range of −(31+QpBdOffset_(Y)) to +32, inclusive.

The syntax slice_qp_delta specifies the initial modification value ofQpY to be used for the coding blocks in the slice until modified by thevalue of CuQpDeltaVal in the coding unit layer. The initial value of theQpY quantization parameter for the slice, SliceQpY, is derived as Eq. 5SliceQpY=31+init_qp_minus31+slice_qp_delta  Eq. 5The value of SliceQp_(Y) shall be in the range of −QpBdOffset_(Y) to+63, inclusive. In an example, the decoder decodes the syntax elementsinit_qp_minus31 and the slice_qp_delta, and uses Eq. 5 to calculate theinitial value for the slice level QP.

In another embodiment, the initial QP value at slice level is set to bea constant value 26, and the syntaxes init_qp_minus26 and slice_qp_deltaare defined.

The syntax init_qp_minus26 plus 26 specifies the initial value ofSliceQpY for each slice referring to the PPS. The initial value ofSliceQp_(Y) is modified at the slice segment layer when a non-zero valueof slice_qp_delta is decoded. The value of init_qp_minus26 shall be inthe range of −(26+QpBdOffsetY) to +37, inclusive.

The syntax slice_qp_delta specifies the initial modification value ofQpY to be used for the coding blocks at the slice segment layer untilmodified by the value of CuQpDeltaVal in the coding unit layer. Theinitial value of the QpY quantization parameter for the slice, SliceQpY,is derived as Eq. 6SliceQpY=26+init_qp_minus26+slice_qp_delta  Eq. 6The value of SliceQpY shall be in the range of −QpBdOffsetY to +63,inclusive. In an example, the decoder decodes the syntax elementsinit_qp_minus26 and the slice_qp_delta, and uses Eq. 6 to calculate theinitial value for the slice level QP.

FIG. 7 shows a flow chart outlining a process (700) according to anembodiment of the disclosure. The process (700) can be used in thereconstruction of a block coded in intra mode, so to generate aprediction block for the block under reconstruction. In variousembodiments, the process (700) are executed by processing circuitry,such as the processing circuitry in the terminal devices (110), (120),(130) and (140), the processing circuitry that performs functions of thevideo encoder (203), the processing circuitry that performs functions ofthe video decoder (210), the processing circuitry that performsfunctions of the video decoder (310), the processing circuitry thatperforms functions of the intra prediction module (352), the processingcircuitry that performs functions of the video encoder (403), theprocessing circuitry that performs functions of the predictor (435), theprocessing circuitry that performs functions of the intra encoder (522),the processing circuitry that performs functions of the intra decoder(672), and the like. In some embodiments, the process (700) isimplemented in software instructions, thus when the processing circuitryexecutes the software instructions, the processing circuitry performsthe process (700). The process starts at (S701) and proceeds to (S710).

At (S710), an adjusted version of an initial QP value at a picture levelfor a picture is decoded from a coded video bitstream. The adjustedversion is in a range with an upper boundary that is changed with amaximum QP value.

At (S720), the initial QP value of a segment is determined based on thesyntax element. The segment can be a slice, a tile, a group of tiles andthe like. In an example, when the syntax element is init_qp_minus26, asum of the value of init_qp_minus26 and 26 is calculated. In an example,when the syntax element is init_qp_minus31, a sum of the value ofinit_qp_minus31 and 31 is calculated. In an example, when non-zero slicedelta qp is decoded, the slice delta qp is added with the sum todetermine the initial QP value at the segment level.

At (S730), the QP value for a block in the segment is determinedaccording to the initial QP value of the segment and adjustmentsassociated with the block. In an example, the block level adjustment,such as the value of CuQpDeltaVal at the coding unit layer, isdetermined. Then, the QP value of the block can be calculated, forexample, as a sum of the QP value for the segment and the value ofCuQpDeltaVal.

At (S740), inverse quantization on quantized data of the block isperformed according to the QP value for the block. Then, samples of theblock are reconstructed based on the results of the inversequantization. Then, the process proceeds to (S799) and terminates.

The techniques described above, can be implemented as computer softwareusing computer-readable instructions and physically stored in one ormore computer-readable media. For example, FIG. 8 shows a computersystem (800) suitable for implementing certain embodiments of thedisclosed subject matter.

The computer software can be coded using any suitable machine code orcomputer language, that may be subject to assembly, compilation,linking, or like mechanisms to create code comprising instructions thatcan be executed directly, or through interpretation, micro-codeexecution, and the like, by one or more computer central processingunits (CPUs), Graphics Processing Units (GPUs), and the like.

The instructions can be executed on various types of computers orcomponents thereof, including, for example, personal computers, tabletcomputers, servers, smartphones, gaming devices, internet of thingsdevices, and the like.

The components shown in FIG. 8 for computer system (800) are exemplaryin nature and are not intended to suggest any limitation as to the scopeof use or functionality of the computer software implementingembodiments of the present disclosure. Neither should the configurationof components be interpreted as having any dependency or requirementrelating to any one or combination of components illustrated in theexemplary embodiment of a computer system (800).

Computer system (800) may include certain human interface input devices.Such a human interface input device may be responsive to input by one ormore human users through, for example, tactile input (such as:keystrokes, swipes, data glove movements), audio input (such as: voice,clapping), visual input (such as: gestures), olfactory input (notdepicted). The human interface devices can also be used to capturecertain media not necessarily directly related to conscious input by ahuman, such as audio (such as: speech, music, ambient sound), images(such as: scanned images, photographic images obtain from a still imagecamera), video (such as two-dimensional video, three-dimensional videoincluding stereoscopic video).

Input human interface devices may include one or more of (only one ofeach depicted): keyboard (801), mouse (802), trackpad (803), touchscreen (810), data-glove (not shown), joystick (805), microphone (806),scanner (807), camera (808).

Computer system (800) may also include certain human interface outputdevices. Such human interface output devices may be stimulating thesenses of one or more human users through, for example, tactile output,sound, light, and smell/taste. Such human interface output devices mayinclude tactile output devices (for example tactile feedback by thetouch-screen (810), data-glove (not shown), or joystick (805), but therecan also be tactile feedback devices that do not serve as inputdevices), audio output devices (such as: speakers (809), headphones (notdepicted)), visual output devices (such as screens (810) to include CRTscreens, LCD screens, plasma screens, OLED screens, each with or withouttouch-screen input capability, each with or without tactile feedbackcapability—some of which may be capable to output two dimensional visualoutput or more than three dimensional output through means such asstereographic output; virtual-reality glasses (not depicted),holographic displays and smoke tanks (not depicted)), and printers (notdepicted).

Computer system (800) can also include human accessible storage devicesand their associated media such as optical media including CD/DVD ROM/RW(820) with CD/DVD or the like media (821), thumb-drive (822), removablehard drive or solid state drive (823), legacy magnetic media such astape and floppy disc (not depicted), specialized ROM/ASIC/PLD baseddevices such as security dongles (not depicted), and the like.

Those skilled in the art should also understand that term “computerreadable media” as used in connection with the presently disclosedsubject matter does not encompass transmission media, carrier waves, orother transitory signals.

Computer system (800) can also include an interface to one or morecommunication networks. Networks can for example be wireless, wireline,optical. Networks can further be local, wide-area, metropolitan,vehicular and industrial, real-time, delay-tolerant, and so on. Examplesof networks include local area networks such as Ethernet, wireless LANs,cellular networks to include GSM, 3G, 4G, 5G, LTE and the like, TVwireline or wireless wide area digital networks to include cable TV,satellite TV, and terrestrial broadcast TV, vehicular and industrial toinclude CANBus, and so forth. Certain networks commonly require externalnetwork interface adapters that attached to certain general purpose dataports or peripheral buses (849) (such as, for example USB ports of thecomputer system (800)); others are commonly integrated into the core ofthe computer system (800) by attachment to a system bus as describedbelow (for example Ethernet interface into a PC computer system orcellular network interface into a smartphone computer system). Using anyof these networks, computer system (800) can communicate with otherentities. Such communication can be uni-directional, receive only (forexample, broadcast TV), uni-directional send-only (for example CANbus tocertain CANbus devices), or bi-directional, for example to othercomputer systems using local or wide area digital networks. Certainprotocols and protocol stacks can be used on each of those networks andnetwork interfaces as described above.

Aforementioned human interface devices, human-accessible storagedevices, and network interfaces can be attached to a core (840) of thecomputer system (800).

The core (840) can include one or more Central Processing Units (CPU)(841), Graphics Processing Units (GPU) (842), specialized programmableprocessing units in the form of Field Programmable Gate Areas (FPGA)(843), hardware accelerators for certain tasks (844), and so forth.These devices, along with Read-only memory (ROM) (845), Random-accessmemory (846), internal mass storage such as internal non-user accessiblehard drives, SSDs, and the like (847), may be connected through a systembus (848). In some computer systems, the system bus (848) can beaccessible in the form of one or more physical plugs to enableextensions by additional CPUs, GPU, and the like. The peripheral devicescan be attached either directly to the core's system bus (848), orthrough a peripheral bus (849). Architectures for a peripheral businclude PCI, USB, and the like.

CPUs (841), GPUs (842), FPGAs (843), and accelerators (844) can executecertain instructions that, in combination, can make up theaforementioned computer code. That computer code can be stored in ROM(845) or RAM (846). Transitional data can be also be stored in RAM(846), whereas permanent data can be stored for example, in the internalmass storage (847). Fast storage and retrieve to any of the memorydevices can be enabled through the use of cache memory, that can beclosely associated with one or more CPU (841), GPU (842), mass storage(847), ROM (845), RAM (846), and the like.

The computer readable media can have computer code thereon forperforming various computer-implemented operations. The media andcomputer code can be those specially designed and constructed for thepurposes of the present disclosure, or they can be of the kind wellknown and available to those having skill in the computer software arts.

As an example and not by way of limitation, the computer system havingarchitecture (800), and specifically the core (840) can providefunctionality as a result of processor(s) (including CPUs, GPUs, FPGA,accelerators, and the like) executing software embodied in one or moretangible, computer-readable media. Such computer-readable media can bemedia associated with user-accessible mass storage as introduced above,as well as certain storage of the core (840) that are of non-transitorynature, such as core-internal mass storage (847) or ROM (845). Thesoftware implementing various embodiments of the present disclosure canbe stored in such devices and executed by core (840). Acomputer-readable medium can include one or more memory devices orchips, according to particular needs. The software can cause the core(840) and specifically the processors therein (including CPU, GPU, FPGA,and the like) to execute particular processes or particular parts ofparticular processes described herein, including defining datastructures stored in RAM (846) and modifying such data structuresaccording to the processes defined by the software. In addition or as analternative, the computer system can provide functionality as a resultof logic hardwired or otherwise embodied in a circuit (for example:accelerator (844)), which can operate in place of or together withsoftware to execute particular processes or particular parts ofparticular processes described herein. Reference to software canencompass logic, and vice versa, where appropriate. Reference to acomputer-readable media can encompass a circuit (such as an integratedcircuit (IC)) storing software for execution, a circuit embodying logicfor execution, or both, where appropriate. The present disclosureencompasses any suitable combination of hardware and software.

APPENDIX A: ACRONYMS

JEM: joint exploration model

VVC: versatile video coding

BMS: benchmark set

MV: Motion Vector

HEVC: High Efficiency Video Coding

SEI: Supplementary Enhancement Information

VUI: Video Usability Information

GOPs: Groups of Pictures

TUs: Transform Units,

PUs: Prediction Units

CTUs: Coding Tree Units

CTBs: Coding Tree Blocks

PBs: Prediction Blocks

HRD: Hypothetical Reference Decoder

SNR: Signal Noise Ratio

CPUs: Central Processing Units

GPUs: Graphics Processing Units

CRT: Cathode Ray Tube

LCD: Liquid-Crystal Display

OLED: Organic Light-Emitting Diode

CD: Compact Disc

DVD: Digital Video Disc

ROM: Read-Only Memory

RAM: Random Access Memory

ASIC: Application-Specific Integrated Circuit

PLD: Programmable Logic Device

LAN: Local Area Network

GSM: Global System for Mobile communications

LTE: Long-Term Evolution

CANBus: Controller Area Network Bus

USB: Universal Serial Bus

PCI: Peripheral Component Interconnect

FPGA: Field Programmable Gate Areas

SSD: solid-state drive

IC: Integrated Circuit

CU: Coding Unit

While this disclosure has described several exemplary embodiments, thereare alterations, permutations, and various substitute equivalents, whichfall within the scope of the disclosure. It will thus be appreciatedthat those skilled in the art will be able to devise numerous systemsand methods which, although not explicitly shown or described herein,embody the principles of the disclosure and are thus within the spiritand scope thereof

What is claimed is:
 1. A method for video encoding in an encoder,comprising: generating a picture level initial quantization parameter(QP) value, an initial QP value for a slice in a picture being a sum ofthe picture level initial QP value and 32; generating an adjustment QPvalue for the slice in the picture; wherein an adjusted initial valuefor the slice being a sum of the initial QP value for the slice in thepicture and the adjustment QP value, the initial QP value for the sliceis in a range of [0, +63], the adjusted initial value for the slice isin a range of [−QpBdOffset, +63], and QpBdOffset represents a value of aluma quantization parameter range offset; performing a quantization ondata of a block in the slice according to a QP value for the block, theQP value for the block being based on the adjusted initial value for theslice; and indicating the picture level initial QP value and theadjustment QP value for the slice in a coded video bitstream.
 2. Themethod of claim 1 wherein the adjusted initial value for the slice isrepresented by SliceQpY,SliceQpY=32+init_qp_minus32+slice_qp_delta, init_qp_minus32 representsthe picture level initial QP value, and slice_qp_delta represents theadjustment QP value for the slice.
 3. The method of claim 2, wherein theQP value for the block is based on SliceQpY and a value of a block-leveladjustment CuQpDeltaVal.
 4. The method of claim 1, wherein the QP valuefor the block is based on the adjusted initial value for the slice and ablock-level adjustment value associated with the block.
 5. The method ofclaim 1, wherein the picture level initial QP value is included in apicture parameter set of the coded video bitstream.
 6. An apparatus forvideo encoding, comprising: processing circuitry configured to: generatea picture level initial quantization parameter (QP) value, an initial QPvalue for a slice in a picture being a sum of the picture level initialQP value and 32; generate an adjustment QP value for the slice in thepicture; wherein an adjusted initial value for the slice being a sum ofthe initial QP value for the slice in the picture and the adjustment QPvalue, the initial QP value for the slice is in a range of [0, +63], theadjusted initial value for the slice is in a range of [−QpBdOffset,+63], and QpBdOffset represents a value of a luma quantization parameterrange offset; perform a quantization on data of a block in the sliceaccording to a QP value for the block, the QP value for the block beingbased on the adjusted initial value for the slice; and indicating thepicture level initial QP value and the adjustment QP value for the slicein a coded video bitstream.
 7. The apparatus of claim 6, wherein theadjusted initial value for the slice is represented by SliceQpY,SliceQpY=32+init_qp_minus32+slice_qp_delta, init_qp_minus32 representsthe picture level initial QP value, and slice_qp_delta represents theadjustment QP value.
 8. The apparatus of claim 7, wherein the QP valuefor the block is based on SliceQpY and a value of a block-leveladjustment CuQpDeltaVal.
 9. The apparatus of claim 6, wherein the QPvalue for the block is based on the adjusted initial value for the sliceand a block-level adjustment value associated with the block.
 10. Theapparatus of claim 6, wherein the picture level initial QP value isincluded in a picture parameter set of the coded video bitstream.
 11. Anon-transitory computer-readable medium storing instructions which whenexecuted by a computer for video decoding cause the computer to perform:generating a picture level initial quantization parameter (QP) value, aninitial QP value for a slice in a picture being a sum of the picturelevel initial QP value and 32; generating an adjustment QP value for theslice in the picture; wherein an adjusted initial value for the slicebeing a sum of the initial QP value for the slice in the picture and theadjustment QP value, the initial QP value for the slice is in a range of[0, +63], the adjusted initial value for the slice is in a range of[−QpBdOffset, +63], and QpBdOffset represents a value of a lumaquantization parameter range offset; performing a quantization on dataof a block in the slice according to a QP value for the block, the QPvalue for the block being based on the adjusted initial value for theslice; and indicating the picture level initial QP value and theadjustment QP value for the slice in a coded video bitstream.
 12. Thenon-transitory computer-readable medium of claim 11, wherein theadjusted initial value for the slice is represented by SliceQpY,SliceQpY=32+init_qp_minus32+slice_qp_delta, init_qp_minus32 representsthe picture level initial QP value, and slice_qp_delta represents theadjustment QP value for the slice.
 13. The non-transitorycomputer-readable medium of claim 12, wherein the QP value for the blockis based on SliceQpY and a value of a block-level adjustmentCuQpDeltaVal.
 14. The non-transitory computer-readable medium of claim11, wherein the QP value for the block is based on the adjusted initialvalue for the slice and a block-level adjustment value associated withthe block.
 15. The non-transitory computer-readable medium of claim 11,wherein the picture level initial QP value is included in a pictureparameter set of the coded video bitstream.